Along with higher densification and higher integration of devices including semiconductor integrated circuits, there is a rapidly increasing demand for stabilization of device operations. In particular, improvement in characteristic values with regard to leakage current, oxide dielectric breakdown strength, and the like is an important problem.
However, even now, the fear of contamination by such undesirable heavy metals as impurities of Cu, Fe, Ni, and the like remains undenied in manufacturing steps for the semiconductor integrated circuit. It is widely known that those heavy metal impurities which exist as a solid solution state in a silicon single crystal significantly deteriorate the above-mentioned characteristics of leakage current and oxide dielectric breakdown strength.
Accordingly, various gettering technologies have been developed as a way to remove those heavy metal impurities out of a device operating region. There are known, for example, an internal gettering (IG) method wherein oxygen atoms contained in a silicon single crystal that has been manufactured through a CZ method are precipitated as oxygen precipitates to capture heavy metals within strains around the precipitates, a method wherein elements of some kind are ion-implanted into a vicinity of device layers to generate intentionally strains or defect layers and heavy metals are gettered into the strains or defect layers, and a method wherein a polycrystalline silicon film is formed on a rear surface of a silicon wafer so as to capture heavy metal impurities with strains generated in polycrystalline grain boundaries.